1. Field of the Invention
The present invention relates to a process for making a lithographic printing plate.
2. Description of the Related Art
In general, a lithographic printing plate is formed from a lipophilic image area for accepting ink and a hydrophilic non-image area for accepting dampening water in a printing process. Lithographic printing is a printing process in which the property of water and printing ink repelling each other is utilized so as to cause a difference in ink attachment on the surface of a lithographic printing plate with a lipophilic image area of the lithographic printing plate as an ink-accepting area and a hydrophilic non-image area as a dampening water-accepting area (non-ink-accepting area), and after inking only the image area ink is transferred to a printing substrate such as paper.
In order to make this lithographic printing plate, a lithographic printing plate precursor (PS plate) formed by providing a lipophilic photosensitive resin layer (photosensitive layer, image recording layer) on a hydrophilic support is widely used in the art. A lithographic printing plate is usually obtained by a process in which, after the lithographic printing plate precursor is exposed through an original image such as a lith film, an area that becomes an image area of the image recording layer is made to remain, and unwanted image recording layer other than this is removed by dissolving using an alkaline developer or an organic solvent to thus form a non-image area in which the surface of the hydrophilic support is exposed.
In this way, in the conventionally known plate-making process of a lithographic printing plate precursor, after the exposure, a step of removing unnecessary image recording layer by dissolving, for example, with a developer is required, but from the viewpoint of the environment and safety carrying out processing with a developer that is closer to neutral or reducing the amount of liquid waste are cited as issues. In particular, since in recent years the disposal of liquid waste discharged accompanying wet treatment has become a great concern throughout the industrial world from the viewpoint of consideration for the global environment, the demand for resolving the above-mentioned issues has been more and more increasing.
On the other hand, digitization techniques involving electronically processing, storing, and outputting image information by computer have been widespread in recent years, and various new image output methods responding to such digitization techniques have been put into practical use. Accompanying this, a computer-to-plate (CTP) technique has been attracting attention in which digitized image information is carried on a highly convergent radiant ray such as laser light and a lithographic printing plate precursor is scan-exposed by this light to directly produce a lithographic printing plate without intervention of a lith film. Therefore, obtaining a lithographic printing precursor suitable for these techniques has become one of the important technological challenges.
As described above, there has been an increasingly strong desire for decreasing the alkalinity of a developer and simplifying the processing step from the viewpoints of both the concerns for the global environment and the conformity with space saving and low running cost.
For example, JP-A-11-65126 (JP-A denotes a Japanese unexamined patent application publication) proposes a development method in which processing is carried out using an aqueous solution having a pH of 8.5 to 11.5.
Furthermore, one embodiment of EP-A-1868036 describes one-bath processing using a processing liquid comprising a water-soluble resin and having a pH of 11.9 to 12.1.
International Patent Application WO 2005/064402 discloses a negative photosensitive composition comprising: (A) an infrared absorber, (B) an organic boron compound which has a function as a polymerization initiator when used in combination with the infrared absorber (A), (C) an onium salt, and (D) a compound having a polymerizable unsaturated group.